Sulphur-containing esters



SULPHUR-CONTAININ G ESTERS Lloyd L. Davis, Bert H. Lincoln, and Gordon D.

Byrkit, Ponca City, Okla., assignors to Continental Oil Company, Ponca City, Okla., a corporation of Delaware No Drawing. Application September 27, 1940, Serial No. 358,697

4 Claims.

Our invention relates to a method of synthesizing sulphur-bearing derivatives of high molecular weight hydrocarbons and more particularly to a method of synthesizing relatively pure high molecular weight sulphur compounds from parafiin hydrocarbons.

This application is a continuation-in-part of our copending application, Serial No. 205,530, filed May 2, 1938.

One object of our invention is to provide a method for synthesizing relatively pure high molecular weight sulphur compounds from petroleum hydrocarbons.

Another object of our invention is to provide a method for converting petroleum fractions and similar hydrocarbons of low value into high molecular weight sulphur compounds of great commercial value.

A further object of our invention is to provide a method of synthesizing high molecular weight sulphur compounds from parafiin hydrocarbons.

Other and further objects of our invention will appear from the following description.

In accordance with our invention, it is now possible to prepare relatively pure sulphur derivatives of the higher paraffin hydrocarbons without being mixed with other sulphur-containing bodies. We first prepare a relatively pure mono-, di-, or trihalogenated parafiin hydrocarbon, free from unhalogenated hydrocarbon and from each other, and convert these relatively pure halogenated hydrocarbons by chemical means into sulphur-containing derivatives.

In the prior art, references are made to monochloro parafiin, dichloro parafiin, trichloro parafiin, and the like usually considering the product of direct chlorination to be the compound represented by the total chlorine content and therefore the desired compounds. We have found that these materials are very crude mixtures of the chlorinated hydrocarbons and contain unchlorinated hydrocarbons and the mono-, di-, and polychloro derivatives and cannot be considered the desired compounds. For example, a so-called trichloro paraflin wax" containing 24 per cent chlorine, which corresponds very closely to the percentage of chlorine in the trichloro compound, was separated by means of crystallization from acetone. The first (least soluble) portion consisting of a mixture of monochloro wax and unchlorinated wax. The percentage of unchlorinated wax in the original mixture was found to be 7.2 per cent. Thus, even a tri-chloro paraffin" as so-called in the prior art because of the total chlorine content. was in fact a crude mixture containing as much as 7.2 per cent of unchlorinated wax and quantities of monoand dichloro waxes, as well as trichloro wax and more highly chlorinated waxes. Its use would not give the same results as a trichloro paraffin free of higher and lower chlorinated paraffin.

Even though the appropriate amount of chlorine is introduced in the wax to form a monochloro wax, we have found that the crude chlorination mixture contains, in addition to small amounts of chlorine and hydrogen chloride and the desired monochlor wax, also unchlorinated wax and more highly chlorinated and less highly chlorinated waxes.

In contrast to the use of such a mixture, we have found it possible, as fully described below, to obtain a relatively pure monochlor compound free from unchlorinated hydrocarbon and free from more highly chlorinated compounds. We may thus prepare (1) monohalogenated hydrocarbons substantially free from unhalogenated hydrocarbons and more highly halogenated hydrocarbons, and (2) dihalogenated hydrocarbons substantially free from unhalogenated hydrocarbons and monohalogenated hydrocarbons, as well as from halogenated hydrocarbons containing more than two atoms of halogen per molecule; (3) trihalogenated hydrocarbons free from halogenated hydrocarbons containing fewer or more than three halogen atoms per molecule and free from unhalogenated hydrocarbons. We refer in this specification to these materials as relatively pure monohalogen compounds, relatively pure dihalogen compounds, etc.

We proved the homogeneity of our relatively pure monochlor wax, for example, by chilling until approximately half of the material had solidified. Solid and liquid portions were separated by a filtration and contained 12.1 and 11.4 per cent chlorine respectively. Our monochloro wax is therefore free from both unchlorinated wax and more highly chlorinated wax. Similarly, we may prepare according to our invention diand polychloro waxes free from unchlorinated wax and monochlor wax, as well as from more highly chlorinated waxes.

The same methods as are described here in detail for the manufacture of relatively pure chlorinated wax are applicable to the manufacture of chlorine derivatives of the parafiin hydrocarbons of higher and lower molecular weight than that represented by the commonly known paraifin wax, including all those paraiiin hydrocarbons whose monochloro derivatives melt lower than the hydrocarbons themselves.

The chlorination of most petroleum hydrocarbons lowers their melting points and, up to a certain point, the greater the extent of chlorination; that is, the more chlorine atoms per molecule, the lower the melting point. The decrease in melting point is stepwise, and this permits us to separate the unchlorinated hydrocarbons from the monochloro hydrocarbons and the monochloro hydrocarbons from the dichloro and higher chlorinated hydrocarbons. We can, for example, separate the unchlorinated wax from the air-. blown mixture by filter pressing at such temperatures that all of the chlorinated waxes are largely liquids, while the unchlorinated waxes are largely solid. The temperature for the pressing operation will depend, of course, on the character of the wax used initially and will vary considerably depending on this factor. For example, at a temperature of from 80 F. to 90 F. the monochloro product formed by the chlorination of wax having a melting point of 120 F. will be liquid, while the unchlorinated wax will be solid, enabling a ready separation to be effected.

Other methods of separation, as for example, sweating, selective solvent extraction at varying temperatures and the like, may be employed for separating solid unchlorinated wax from chlorinated portions, and for separating the monochloro wax from the more highly chlorinated portions.

The unchlorinated wax separated from the crude chlorination mixture may be recycled to obtain further quantities of chlorinated waxes. It does not represent refractory material, and the same proportions of chlorination products are obtained from it as from fresh wax.

The liquid chlorinated waxes consist largely of monochloro and dichloro waxes when approximately or 20 per cent chlorine respectively is introduced into a starting wax of, say, from 115 to 130 F. melting point, but some polychloro wax may be present. These monoand dichloro waxes may be separated from each other by crystallization from acetone, using about 12 /2 gallons of acetone per 100 pounds of crude chlorinated waxes. In preparing the solution, an elevated temperature is employed to insure that the chloro waxes are completely dissolved in the solvent. The solution is then chilled to a temperature of between minus 15 F. to minus F. when a parafiin wax of 115 to 130 F. melting point is used for the initial chlorination. The monochloro waxes are precipitated out nearly quantitatively, while the dichloro and polychloro waxes will remain in solution. The precipitated monochloro waxes may be readily separated by settling, filtering, or centrifuging.

We have also used other crystallization solvents such as methyl-ethyl ketone, acetone, benzene, acetone-methylene chloride, and various halogenated solvents. The use of a particular one or combination of these solvents requires the experimental determination of the proper proportions and temperatures necessary to obtain the desired separation of the crude chlorination mixture into the various stages of chlorine contents. Halogenated solvents serve to aid in the precipitation of unchlorinated wax, while benzene increases the solubility of the more highly chlorinated materials.

On further chilling of the solution, or by evaporating off part of the solvent and again chiliing, the dichloro and polychloro waxes may be similarly separated.

In this manner, the crude chlorination mixture may be separated into unchlorinated wax, monochloro wax, dichloro, and polychloro wax. It is to be understood, of course, that the separation conditions will vary depending upon the melting point of the starting material.

In preparing monochloro wax, for example, the separated monochloro wax will be found to contain approximately the theoretical chlorine content. In the case of the wax which had the F. melting point, batches showed chlorine content of 10.2 per cent, 10.5 per cent, 10.3 per cent, and 10.8 per cent. These are very close to the theoretical chlorine content of 10.0 per cent. This monochlor wax is substantially free from unchlorinated waxes and polychloro waxes.

Our paraffin hydrocarbons are preferably obtained from petroleum. Any source of materials, rich in hydrocarbons of the methane or CnH2n+2 series, or mixtures relatively rich in these components, may be used as starting materials in practicing our invention. The method of our invention is particularly applicable to the higher parafiin hydrocarbons but is eminently satisfactory on all those hydrocarbons whose monochloro derivatives melt lower than the hydrocarbons themselves. While the product of the preferred embodiment of our invention is a mixture, the monochloro derivatives prepared according to our invention are free from unchlorinated and more highly chlorinated material. The dichloro derivatives are free from unchlorinated hydrocarbons, monochlorinated hydrocarbons, and more highly chlorinated hydrocarbons. The purity of the final product with respect to homologues is determined by the purity of the starting hydrocarbon. It is understood, of course, that when a pure hydrocarbon is employed, a correspondingly pure halide is obtained.

Having selected the hydrocarbon in accordance with the desired final product, we chlorinate the hydrocarbon until approximately that amount of chlorine is absorbed which will produce the monochloro compound when that is the desired product, or approximately that amount of chlorine which will produce the dichloro compound when that is the desired product, etc.

In the case of paraflin hydrocarbons having from 18 to 24 carbon atoms per molecule; that is, a material having a melting point of approximately 120 F., about 10 per cent added chlorine will produce substantially the equivalent of the monochloro product. The amount of chlorination may vary between 8 per cent and 12 per cent without being disadvantageous. The percentage of chlorine introduced into the hydrocarbon just described will be approximately 17 per cent when a dichloro product is desired. The amount of chlorine introduced will be less in the case of the high molecular weight, higher melting hydrocarbons, and more in the case of the lower molecular weight, lower melting hydrocarbons, for a given number of chlorine atoms per molecule. The chlorination may be accomplished in any suitable manner. We prefer to heat the hydrocarbon to a temperature at least that of its melting point and pass chlorine gas through the melted hydrocarbon. Agitation increases the efficiency of chlorine absorption but is not essential. The chlorination reaction is exothermic and the heat of reaction is ordinarily ample to maintain the mixture in the liquid state without the addition of other heat. Large quantities of hydrogen chloride gas are evolved which are conducted from the reaction chamber, together with unreacted chlorine. The material being chlorinated is constantly weighed while the chlorination is in progress, in order to determine the extent of chlorination as indicated above. Samples may be removed from time to time, and the specific gravity of these may be determined in order to follow the chlorination process. If desired, chlorine analyses may be conducted on samples of the material being chlorinated. After sufficient chlorine has been introduced, we blow the mixture with air or an inert gas, such as carbon dioxide, until the hydrogen chloride and free chloride, if any, are substantially removed.

As an example of the manufacture of a relatively pure chlorinated hydrocarbon, we describe here the manufacture of a relatively pure monochloro wax which contains approximately 26 carbon atoms per molecule. We started with 723.4 parts of a hydrocarbon wax having a melting point of 120 F. The wax was chlorinated until 72.5 parts by weight of chlorin had been absorbed. The chlorinated wax was air-blown to remove hydrochloric acid and uncombined residual chlorine, and then pressed at 85 F. The unchlorinated wax was reserved for further chlorination. The liquid portion was then dissolved in acetone, 350 parts of crude chloro wax being dissolved in 3,226 parts of acetone. The solution was chilled to minus 18 F. and 185 parts by weight of solid monochloro wax containing 10.3 per cent chlorine was precipitated. Monochlor wax from this paraflin wax contains theoretically 10.0 per cent chlorine. The monochloro wax was normally liquid at room temperatures.

Dichloro waxes and polychloro waxes prepared according to our method are suitable for use in any of the applications described in the prior art, where such dichloro waxes and polychloro waxes are required. Since they contain no unchlorinated wax or lower chlorinated waxes, they are particularly efiicient in these applications and are a distinct improvement over the prior art which used crude chlorination mixtures of approximately the proper chlorine content but which consisted of unchlorinated wax and more highly chlorinated wax.

While chlorine has been referred to above almost exclusively, it is to be understood that any of the halogens are suitable to make halogen derivatives of the parafiin hydrocarbons according to our method. This bromine, iodine, and fluorine may suitably be used to obtain the corresponding bromides, iodides and fluorides. For some purposes to which the halides are to be put, the bromine compounds are much to be desired over the chlorine compounds, since they are considerably more reactive. Where this is the case, we halogenate with bromine, using a halogen carrier, such as halides of antimony, phosphorus, iron, various metals and the like, and separate the brominated mixture into its components as described above in the case of the chlorine compounds. The iodine compounds of the paraffin hydrocarbons may be prepared by direct iodination or by an indirect method. By the indirect method, the above described separation of mono-, di-, and polyhalogen derivatives maybe employed in any step of the process. Thus we may separate a relatively pure mono or dichloro parafiln and convert it to the corresponding iodine compound, or we may convert the crude halogenated mixture into a crude iodlnated mixture and then separate into the various stages of halogenation. Fluorine may be introduced into paraffln hydrocarbons directly or indirectly by analogous methods. For most purposes, however, we prefer to use the chlorine compounds on account of the cheapness and availability of chlorine above all the other halogens.

In preparing sulphur-bearing derivatives of the higher aliphatic hydrocarbons, we treat chemically the relatively pure halogenated hydrocarbons by hydrolytic methods to obtain the corresponding hydroxyl compounds which may be alcohols, glycols, or higher hydroxylated materials according to the number of halogen atoms present in the halogen compound. The derivatives and methods of preparing may be classified as, follows: 117?! r -i 1;

By the action of thionyl chloride on the alcohols.

2. sulfates: By the action of SOzClz on the alcohols or by oxidation of sulfites.

3. Xanthates: By the action of CS2 and caustic alkalies on the alcohols.

, 4. Thiosulfates: From the sulfites and sulfur.

5. Thiophosphates: From the alcohols and thiophosphoryl chloride (PSCh) 6. Thioketones: The alcohols are readily oxidized to ketones which when treated with sulfides of phosphorus yield thioketones.

If our monohalogenated hydrocarbons be hydrolyzed to the corresponding alcohols, these are useful for various sulphur and oiqrgen-bearing derivatives of high molecular weight. Esters of these alcohols with sulphur-containing inorganic and organic acids are particularly interesting. By means of thionyl chloride, the alkyl sulfites of the type, R2803 may be formed. These when treated witirtli' theoretical quantity of elemental sulphur are conve into the corresponding thiosulfates, "RzS2Oa. may be used to pr eir sulfates through the action of sulfuryl chloride, or chlorosulfonic acid. The sulfates may also be prepared by the oxidation of the corresponding sulfites.

In preparing esters of sulfur containing organic acids, we first prepare the alcohol corresponding to our relatively pure monochlor (or monobrom) wax:

Example 1 A mixture of 386 parts of the monochlor wax prepared substantially as described above, 44 parts of caustic soda, and 400 parts of water are agitated thoroughly and heated to 400 F. under pressure for eight hours. The alcohol is separated, washed, and dried.

Example 2 We add 368 parts of this alcohol to 60 parts of boiling thionyl chloride and maintain the temperature of the mixture at 200 F. for five hours. The sulfite is then washed with water and dried.

Thiophosphates of the higher alcohols are produced by the action of thiophosphoryl chloride, PSCla. These products are useful addends to lubricants of all sorts.

Example 3 We reflux a mixture of 1,100 parts of the alcohol of Example 1 with 1'70 parts of thiophosphoryl chloride in 2,000 parts of xylene for eight hours, wash with water, and then dry. On distilling oil the xylene, we obtain our higher alkyl thiophosphate.

When refluxed with caustic alkalies and carbon bisulfides, the higher alcohols give rise to the alkyl xanthates, for example, octadecyl xanthate, pentacosyl xanthate, and the like.

Example 4 We pass chlorine into a commercial grade of octadecane until the weight of 254 parts has increased to 290 parts. The crude chlorination mixture, after air-blowing, is dissolved in acetone, using four times as much acetone by weight as of the chlorination mixture. n cooling to 40 F. most of the unchlorinated hydrocarbon separates and is removed by filtration. The filtrate is cooled to -20 F. and the monochlorinated hydrocarbon removed similarly. It is a liquid at room temperature.

Example 5 We heat at 400 F. in an autoclave, 145 parts of the monchlor octadecane, 22 parts of caustic soda, and 200 parts of water at 350 F. for five hours. The octadecanol is separated, washed, and dried.

Example 6 We dissolve 2'70 parts of octadecanol in 1,000 parts of xylene and heat with 25 parts of sodium until the latter dissolves. To the solution, we add 150 parts of carbon blsulfide and heat the mixture at 300 F. under pressure for four hours. On cooling, we wash out the sodium octadecyl xanthate with water and evaporate the solution to obtain our product.

The high molecular weight alcohols and other oxygen derivatives of paraffin hydrocarbons. such as ketones, aldehydes, esters, amides, and the like, may be converted into compounds in which more or less of the oxygen is replaced by sulphur. Such transformations may be accomplished by heating the oxygen derivative with phosphorus trisulfide or pentasulfide. Some of these reactions proceed without solvent, but in general it is advantageous to use an inert solvent such as benzene or xylene together with good stirring at a suitable reaction temperature. It will be apparent that the solvent must be selected so as to permit of the use of an adequate reaction temperature.

Example 7 We heat 368 parts of the alcohol described in Example 1 to 250 F. and pass dry air through it, absorbing the water from effluent gas until 18 parts have been absorbed. The product is essentially the high molecular weight ketone of the same molecular weight -as the starting material.

Example 8 Into 1,000 parts of xylene, we introduce 366 parts of the ketone of Example 7 and 100 parts of phosphorus trisulfide and boil the mixture for six hours. The solid material is filtered off and the xylene distilled from the residual thioketone.

It is to be understood that any or all of the reactions here described may be carried out under atmospheric or superatmospheric pressure.

It will be seen that we have accomplished the purpose of our invention; namely, to provide relatively pure sulphur-bearing derivatives of high molecular weight parafiin hydrocarbons, each substantially free from other types of sulphur compounds and from unreacted paraffin hydrocarbons.

Having thus described our invention we claim:

1. A method for the synthesis of sulphurbearing derivatives of high molecular weight, including the steps of halogenating paraflinic hydrocarbons whose monochloro derivatives melt lower than the hydrocarbons themselves. separating relatively pure halogenated hydrocarbons from the crude halogenated mixture, hydrolyzing the pure halogenated hydrocarbon with an alkaline reagent and introducing a sulphur-bearing group by reacting the hydroxylated material with a material selected from the group consisting of thiophosphoryl chloride, thionyl chloride and sulphuryl chloride.

2. A method for the synthesis of sulphurbearing derivatives of high molecular weight. including the steps of halogenating paraflinic hydrocarbons whose monochloro derivatives melt lower than the hydrocarbons themselves, separating a relatively pure halogenated hydrocarbon from the crude halogenated mixture, replacing the halogen of said relatively pure halogenated hydrocarbon with hydroxyl groups by means of an alkaline reagent and introducing a sulphurbearing group by reacting the hydroxylated material with thiophosphoryl chloride.

3. A method for the synthesis of sulphurbearing derivatives of high molecular weight, including the steps of halogenating parafiinic hydrocarbons whose monochloro derivatives melt lower than the hydrocarbons themselves, separating a relatively pure halogenated hydrocarbon from the crude halogenated mixture, replacing the halogen of said relatively pure halogenated hydrocarbon with hydroxyl groups by means of an alkaline reagent and introducing a sulphurbearing group by reacting the hydroxylated material with thionyl chloride.

4. A method for the synthesis of sulphurbearing derivatives of high molecular weight, including the steps of halogenating parafiinic hydrocarbons whose monochloro derivatives melt lower than the hydrocarbons themselves, separating a relatively pure halogenated hydrocarbon from the crude halogenated mixture, replacing the halogen of said relatively pure halogenated hydrocarbon with hydroxyl groups by means of an alkaline reagent and introducing a sulphurbearing group by reacting the hydroxylated material with sulphuryl chloride.

LLOYD L. DAVIS. BERT H. LINCOLN. GORDON D. BYRKIT. 

